U.S. patent number 6,679,315 [Application Number 10/047,871] was granted by the patent office on 2004-01-20 for small scale chip cooler assembly.
This patent grant is currently assigned to Marconi Communications, Inc.. Invention is credited to Michael R. Cosley, Richard L. Fischer, Jack H. Thiesen, Gary S. Willen.
United States Patent |
6,679,315 |
Cosley , et al. |
January 20, 2004 |
Small scale chip cooler assembly
Abstract
A microscale chip cooling system for a heat dissipating item,
such as Intel's Pentium brand microprocessor. The system includes a
40 millimeter by 40 millimeter thermally insulated housing
including a base and a cover. The system also includes a thermally
conductive evaporator. The evaporator is adapted to be attached to
a heat source such as the microprocessor. The cover includes inlet
and outlet ports and the base includes a capillary passage. A
refrigerant or heat transferring fluid is pumped or past through
the passage before making a sudden expansion in an expansion zone
just before passing to an evaporator chamber. Pool and flow boiling
and forced convection may occur in the evaporator chamber as heat
is transferred from the microprocessor through the thermally
conductive evaporator to the refrigerant. The refrigerant then
returns to a compressor to repeat the cycle. The system is
extremely small and very efficient.
Inventors: |
Cosley; Michael R. (Crystal
lake, IL), Fischer; Richard L. (Lisle, IL), Thiesen; Jack
H. (Longmont, CO), Willen; Gary S. (Boulder, CO) |
Assignee: |
Marconi Communications, Inc.
(Cleveland, OH)
|
Family
ID: |
21951479 |
Appl.
No.: |
10/047,871 |
Filed: |
January 14, 2002 |
Current U.S.
Class: |
165/80.4;
165/104.21; 361/699; 361/700; 257/715; 165/104.26; 165/168;
257/E23.098 |
Current CPC
Class: |
F25B
41/37 (20210101); F28F 3/02 (20130101); H01L
23/473 (20130101); F28F 3/12 (20130101); F25B
39/022 (20130101); H05K 1/0203 (20130101); H05K
1/0209 (20130101); H01L 2924/0002 (20130101); F28F
2260/02 (20130101); F28D 2021/0071 (20130101); F28D
2021/0029 (20130101); H01L 2924/0002 (20130101); H01L
2924/00 (20130101) |
Current International
Class: |
F28F
3/00 (20060101); F28F 3/02 (20060101); F25B
41/06 (20060101); F25B 39/02 (20060101); H01L
23/473 (20060101); H01L 23/34 (20060101); F28F
007/00 (); F28D 015/00 (); H05K 007/20 (); H01L
023/34 () |
Field of
Search: |
;165/80.4,104.26,104.33,104.21,168 ;361/699,700 ;62/515
;257/714,715 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Little William, Mar. 1978, IBM Corp, vol. 20 No. 10. p. 3919.*
.
"Pool Boiling Heat Transfer From Plain and Microporous, Square
Pin-Finned Surfaces in Saturated FC-72"; K.N. Rainey and S.M. You;
Journal of Heat Transfer, vol. 122, pp. 509-516, Aug. 2000. .
"Effects of Perpendicular Flow Entry on Convective Heat/Mass
Transfer From Pin-Fin Arrays"; Chyu et al.; Journal of Heat
Transfer; vol. 121, pp. 668-674, Aug. 1999. .
"Pool Boiling Heat Transfer With an Array of Flush-Mounted, Square
Heaters on a Vertical Surface"; S.M. You et al; Journal of
Electronic Packaging; vol. 119, pp. 17-24, Mar. 1997. .
"Combined Pressure and Subcooling Effects on Pool Boiling From a
PPGA Chip Package"; A.A. Watwe et al; Journal of Electronic
Packaging, vol. 199, pp. 95-105, Jun. 1997. .
"Analytic Modeling, Optimization, and Realization of Cooling
Devices in Silicon Technology"; Perret et al.; IEEE Transactions on
Components and Packaging Technologies, vol. 23, No. 4, pp. 665-671,
Dec. 2000. .
"An Electrodynamic Polarization Micropump for Electronic Cooling";
J. Darabi and D. DeVoe; Journal of Microelectromechanical Systems,
vol. 10, No. 1, pp. 98-106, Mar. 2001. .
"Heat Transfer from Micro-Finned and Flat Surfaces to Flow of
Fluorinert Coolant; Boiling Heat Transfer"; Mizunuma et al.; 1998
InterSociety Conference on Thermal Phenomena, pp. 386-391, Aug.
1998. .
"Imersion Cooling of Electronics in Fluidized Beds of Dielectric
Particles"; Robert C. Brown and Scott S. Jasper; Heat Transfer
Engineering, vol. 10, No. 3 pp. 36-42, 1989. .
"Optimal Structure for Microgrooved Cooling Fin fo High-Power LSI
Devices"; S. Sasaki and T. Kishimoto; Electronics & Mechanics
Technology Laboratories, Oct. 21, 1986. .
"Gas Cooling Enhancement Technology for Integrated Circuit Chips";
Kishimoto et al.; IEEE Transactions of Components, Hybrids, and
Manufacturing Technology, vol. CHMT-7, No. 3, pp. 286-293, Sep.
1984. .
"The Effect of Tip Convection on the Performance and Optimum
Dimensions of Cooling Fins"; K. Laor and H. Kalman; Int. Comm. Heat
mass Transfer, vol. 19, pp. 569-584, 1992..
|
Primary Examiner: Bennett; Henry
Assistant Examiner: Duong; Tho V
Attorney, Agent or Firm: Jones Day
Claims
What is claimed is:
1. A microscale cooling system comprising: a thermally insulative
housing operatively connected to an inlet port and an outlet port;
a capillary passage formed downstream of said inlet port within
said housing; a thermally conductive element connected to said
housing, said thermally conductive element forming with said
housing a pool boiling chamber and an expansion zone; and a
plurality of thermally conductive projections mounted to said
thermally conductive element and extending into said pool boiling
chamber wherein heat transferring fluid flowing from said capillary
passage cools in said expansion zone before absorbing heat in said
pool boiling chamber.
2. The system as claimed in claim 1 wherein: said thermally
conductive element includes an outside surface adapted to be
connected to a microscale heat generating device.
3. The system as claimed in claim 2 wherein: pressure at said inlet
port is about 55 psi, flow rate of a heat transferring fluid is
about 0.0005 kilograms per second, said capillary passage is about
two inches long with a square cross section of about 0.250
millimeters per side and said thermally insulative housing and
connected thermally conductive element has outer dimensions of
about forty millimeters in length, about forty millimeters in width
and about seven millimeters in height.
4. The system as claimed in claim 3 wherein: each of said plurality
of projections in the pool boiling chamber is about one millimeter
square in cross section and about five millimeters long.
5. A microscale cooling system comprising: a thermally insulative
housing having an inlet port and an outlet port; a capillary
passage formed downstream of said inlet port within said housing; a
thermally conductive element connected to said housing, said
thermally conductive element forming with said housing a pool
boiling chamber; and a plurality of thermally conductive
projections mounted to said thermally conductive element and
extending into said pool boiling chamber wherein heat transferring
fluid is throttled in said capillary passage and absorbs heat in
said pool boiling chamber.
6. The system as claimed in claim 5 wherein: said thermally
conductive element includes an outside surface adapted to be
connected to a microscale heat generating device.
7. The system as claimed in claim 6 wherein: pressure at said inlet
port is about 55 psi, flow rate of a heat transferring fluid is
about 0.0005 kilograms per second, said capillary passage is about
two inches long with a square cross section of about 0.250
millimeters per side and said thermally insulative housing and
connected thermally conductive element has outer dimensions of
about forty millimeters in length, about forty millimeters in width
and about seven millimeters in height.
8. The system as claimed in claim 6 wherein: each of said plurality
of projections in the pool boiling chamber is about one millimeter
square in cross section and about five millimeters long.
9. A microscale cooling system comprising: a housing formed of
thermally insulative materials; a thermally conductive structure
connected to said housing, said thermally conductive structure
forming with said housing a chamber; and a single capillary passage
formed in said housing and in communication with said chamber; and
wherein said thermally conductive structure includes an outer
surface for connecting to a heat generating device; said thermally
conductive structure includes a plurality of projections; and said
chamber is a pool boiling chamber.
10. The system as claimed in claim 9 wherein: said plurality of
projections are aligned in rows.
11. The system as claimed in claim 10 wherein: said plurality of
projections are obliquely aligned.
12. A microscale cooling system comprising: a first housing layer
of thermally insulative material having a first portion and a
second portion; an exposed elongated fluid passage formed in said
first portion of said first housing layer; a second housing layer
of thermally insulative material having an inlet port, an outlet
port, a mating surface and an absence of an elongated fluid
passage, said mating surface of said second housing layer being
attached to said first portion of said first housing layer for
enclosing said elongated fluid passage to form a capillary of
predetermined cross section and length; a third layer formed of
thermally conductive material attached to said second portion of
said first housing layer and forming with a wall of said first
housing layer a chamber, said third layer having first and second
surfaces; a plurality of small, cross-sectioned projections
extending from said first surface of said third layer into said
chamber constructed to engage a fluid flowing from said capillary
wherein heat is transferred from said projections to said fluid;
and a fourth layer of thermally conductive material attached to
said second surface of said third layer for connecting a heat
generating electronic device to said third layer.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chip cooling assembly and more
particularly to a very small-scale chip cooling assembly for
efficiently and effectively cooling small but powerful electronic
microprocessors or other small, heat generating devices.
2. Description of the Related Art
As microprocessors, such as Intel's Pentium brand series, become
more powerful, they also generate more heat. To prevent failure and
to ensure optimum capability, it is necessary to remove heat and to
maintain the temperature of these microprocessors within a
predetermined range. A number of different devices trying to
accomplish this have been patented. These include the use of cold
plates, microchannels, impingement jets and variations and
combinations of these as well as other cooling devices. See for
example, U.S. Pat. Nos. 4,392,362; 4,941,530; 5,183,104; 5,169,372;
5,394,936; 5,544,696; 5,696,405; and 5,870,823. The search,
however, goes on for more effective, efficient and reliable cooling
mechanisms.
BRIEF SUMMARY OF THE INVENTION
The below described embodiment improves upon the prior efforts and
is a small scale cooler system comprising a housing, an inlet port
formed in the housing for receiving a refrigerant or similar fluid,
an outlet port formed in the housing, a thermally conductive
element connected to the housing, an evaporator chamber operatively
communicating with the housing where heat exchange takes place, a
capillary passage formed in the housing extending downstream from
the inlet port, and an expansion zone formed downstream of the
capillary passage and in fluid communication with the evaporator
chamber.
There are a number of advantages, features and objects achieved
with the present invention which are believed not to be available
in earlier related devices. For example, one advantage is that the
present invention provides a very effective cooling system for very
small heat dissipating items, such as electronic microprocessors.
Another object of the present invention is to provide a small
cooling system which is simple, reliable and economical. Yet
another feature of the present invention is to provide a cooling
system which is very small scale and easily attached to a small
heat generating device. Yet a further feature of the present
invention is to provide a cooling system flexible enough to
transfer heat by forced convection, flow boiling, and pool boiling
and any combination thereof.
A more complete understanding of the present invention and other
objects, advantages and features thereof will be gained from a
consideration of the following description of the preferred
embodiment read in conjunction with the accompanying drawing
provided herein.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIG. 1 is a top plan view of the cooling assembly described
hereinbelow.
FIG. 2 is a side elevation view of the cooling assembly.
FIG. 3 is a bottom plan view of the cooling assembly.
FIG. 4 is a front elevation view of the cooling assembly.
FIG. 5 is a top view of a cover of the cooling assembly rotated 180
degrees from that shown in FIG. 1.
FIG. 6 is a side elevation view of the cover.
FIG. 7 is a rear elevation view of the cover.
FIG. 8 is a top plan view of a base member of the cooling assembly
shown in FIG. 1.
FIG. 9 is a side elevation view of the base.
FIG. 10 is a bottom plan view of the base.
FIG. 11 is a rear elevation view of the base.
FIG. 12 is a top plan view of a thermally conductive element of the
cooling assembly shown in FIG. 1.
FIG. 13 is a side elevation view of the thermally conductive
element.
FIG. 14 is a bottom plan view of the thermally conductive
element.
FIG. 15 is a front elevation view of the thermally conductive
element.
FIG. 16 is a sectional isometric view of the cooling assembly.
FIG. 17 is an exploded isometric view of the cooling assembly.
FIG. 18 is an exploded isometric view of a cooling assembly having
a construction different from that of the FIG. 1 embodiment.
DETAILED DESCRIPTION OF THE INVENTION
While the present invention is open to various modifications and
alternative constructions, the preferred embodiment shown in the
drawing will be described herein in detail. It is understood,
however, that there is no intention to limit the invention to the
particular form disclosed. On the contrary, the intention is to
cover all modifications, equivalent structures and methods, and
alternative constructions falling within the spirit and scope of
the invention as expressed in the appended claims.
As used here, the term "microscale" refers to a very small scale
consistent with the size of microchips, such as Intel's Pentium
brand processor. A synonym of microscale is "mesoscale." The term
"microsystem" refers directly to a microchip such as the Pentium
brand processor. The reference to the Pentium brand processor is
not to be considered limiting in any way and other microprocessors
may be substituted. Also, future microprocessors of the same,
similar, smaller or even larger size are considered within the
scope, range and extent of the present invention. The term "pool
boiling" involves the technology of boiling heat transfer and is a
term well known by those skilled in the art. The term also appears
in research articles such as the article, "Pool Boiling Heat
Transfer From Plain And Microporous, Square Pin-Finned Surfaces In
Saturated FC-72." This article appeared in the August, 2000 edition
of the Journal of Heat Transfer, pages 509-516.
Referring now to FIGS. 1-4, an example of the claimed invention, in
the form of a microscale cooling system 20, is illustrated. The
system includes a housing 22, which is itself comprised of a cover
24 and a base 26. The system also includes an evaporator 28.
Mounted to the cover are an inlet fitting 30 and an outlet fitting
32. The cover and base are made of any suitable thermally
insulating synthetic resin, such as Nylon 6 or PBT. By the term
"thermally insulating", it is meant a material having low thermal
conductivity. The cover and base act as an insulator for
refrigerant or other heat transferring fluid, liquid and gas
flowing within the assembly. Formed between the base and the
evaporator is an evaporator chamber to be described below.
The cover 24 is a generally flat plate having two holes 34, 36,
FIGS. 5-7, for forming inlet and outlet ports, respectively. The
cover includes an outside surface 38 and an inside surface 40.
Mounted to the cover on the outside surface are the inlet fitting
30 and the outlet fitting 32, FIGS. 1, 2 and 4. Also mounted to or
formed on the outside surface of the cover are a series of paired
grooming clips 44, 46, 48, 50, 52, 54 for aligning and constraining
conduits (not shown) supplying a refrigerant or fluid for absorbing
heat and conduits for carrying away gas phase refrigerant or other
gas phase product back to a compressor as will be explained below.
The cover is generally square with each side measuring about forty
millimeters. The cover may be 0.5 to 1.0 millimeter thick. Attached
to the evaporator 28 by a thermally conductive adhesive tape or the
like 51 is a microscale heat generating device, such as a
microprocessor 53. Because the evaporator is formed of heat
conducting material, as described below, heat from the
microprocessor is conducted to the evaporator.
Referring now to FIGS. 8-11, the base 26 is also a generally flat
plate having first surface 56 and second surface 58. The first
surface 56 abuts and is sealed to the inside surface 40 of the
cover. Formed in the first surface of the base is a capillary
passage 60 having as a top wall the inside surface 40 of the cover
24. The capillary passage has an upstream end 62 and a downstream
end 64. The upstream end 62 aligns with the inlet port 34 of the
cover 24 so that liquid pumped to the inlet port enters the
capillary passage 60. The capillary passage may be serpentine to
allow its length to be adjusted as desired by forming more or less
loops. The length of the capillary passage depends upon the fluid
used and the heat lift capacity desired as well as other factors.
The cross-sectional dimensions of the capillary passage are also
related to the length of the capillary passage. They balance flow,
ability to pump and provide the required pressure drop. The
downstream end 64 of the capillary passage adjoins an opening 66 in
the base 26. The capillary passage may be formed in the base by
molding or by hot embossing or by any other convenient
manufacturing technique known or developed in the future.
Generally, the capillary passage is square shaped in cross section
having a side dimension of about two hundred fifty microns. The
passage may be semicircular or trapezoidal in shape and corners may
have a radius. The base 26 may have a thickness of about one
millimeter.
The base 26 also includes a second opening 68 which aligns with an
elongated recess 70. A far end portion 72 of the recess aligns with
the outlet port 36, FIG. 5, in the cover 24. The base may also
includes a sealing ridge 74 around the periphery of the first
surface 56. The sealing ridge facilitates assembly of the cover to
the base by ultrasonic welding, laser welding or RF welding,
processes which are well known to those skilled in the art.
Extending from the second surface 58 is a mounting flange 76. The
flange 76 will engage a lip of the evaporator 28, FIG. 3, as will
be explained below. The mounting flange has an oblong hexagonal
shape as is readily seen in FIG. 10.
The fluid referred to above may be any heat transferring fluid
including a refrigerant, such as those known as R236fa, R123,
R134a, R124, or CO.sub.2. Also, any suitable dielectric fluid or
other suitable refrigerant may be used as is well known to those
skilled in the refrigerant art. Further, other heat transferring
fluids may be used, such as DYNALENE, FLUORINET, NOVEC, FLUTEC and
a liquid slurry with encapsulated phos change materials (PCM). As
is also well understood to those skilled in the art, the liquid is
formed by compressing a gas to its liquid phase and then cooling
the liquid before being exposed to heat. Upon the transfer of heat,
the liquid again returns to a gas phase, or the liquid is pumped in
and picks up heat via forced convection (remains liquid) or by flow
or pool boiling where it becomes a gas or gas mixture which is
later condensed back to a liquid. Other fluids can also be used as
is well known to those skilled in the art.
The evaporator 28 is a thermally conductive element in the form of
a metal plate 80 with a number of projections or fins 82, as they
are usually called, mounted to an inside surface 84. An outside
surface 86 of the evaporator is generally flat and is adapted to be
connected to a heat source such as a microprocessor. The evaporator
may also be connected to other small heat generating mechanisms,
such as transistors, power semiconductors, laser optical IGBTs or
other electronic or opto-electronic devices. The term "microsystem"
is used here to refer to all such items and others, whether now in
existence or developed in the future. The evaporator is formed of a
material having high thermal conductivity, such as copper or
aluminum. The evaporator is attached to the base by an convenient
means, such as molding the base to the evaporator or using other
techniques known by those in the art. The evaporator 28 includes a
lip 88 around its periphery which may form an interference fit with
the mounting flange 76 of the base 26. See also FIG. 16. The
evaporator may be connected to a microsystem by a thermal adhesive,
thermal pad, or an evaporator may be molded or formed as a part of
the microsystem should that prove more effective or efficient. (See
FIG. 2.) All of these are commercially available and add
considerable flexibility to the design.
An evaporator chamber 90, FIGS. 16 and 17, is formed between the
evaporator 28 and the base 26, downstream of the capillary passage
60 and upstream of the outlet port 36 and among the fins 82. An
expansion zone 92 is also formed between the evaporator and the
base, and more particularly immediately downstream of the opening
66. The expansion zone is also immediately upstream of the
evaporator chamber 90. This allows liquid in the capillary passage
to cool in the expansion zone 92 and then pass into the evaporator
chamber where pool boiling occurs among the fins.
When passing through the evaporator chamber, the heat transferring
fluid will change phase to a gas or remain liquid when absorbing
heat from the evaporator. The gas or liquid proceeds to a
collection region 94 downstream of the evaporator chamber before
exiting through the outlet port 36 and back to a compressor, not
shown.
Referring now to FIG. 18, a cooling system 100 with a slightly
different construction is disclosed. A housing 101 includes a base
102 and a cover 104. Inlet and outlet fittings 106, 108 are located
in inlet and outlet ports 110, 112, respectively. A capillary tube
113 is connected to the inlet fitting 106. An expansion port 114 is
formed in the base 102 and an evaporator chamber 116 is also formed
in the base. An upper wall of the evaporator chamber is formed by
the cover 104. A lower wall of the evaporator chamber is formed by
an evaporator 118 and includes a plate 120 with a multitude of fins
122. Downstream of the evaporator chamber is a region 124 which
includes upstanding blocks, such as the block 126 which alternate
with passageways between the blocks, such as the passageway 128.
The blocks form multiple exhaust ports to help separate flow to
make more efficient use of the evaporator, to minimize orientation
effects, to reduce pressure drop and to minimize blockage due to
contamination. Downstream of the blocks is a passage 130 which is
upstream of the outlet port 112. Like the assembly in FIG. 1, the
construction of FIG. 18 includes a high thermally conductive
evaporator and low thermally conductive cover and base.
In operation, the refrigerant is at a high pressure state when
delivered to the inlet fitting 30, FIG. 17. In a construction where
R236 is the refrigerant and a heat lift of 50 watts is sought, the
inlet pressure is about 55 psi, the flow rate is about 0.00055
kilograms per second and the capillary passage 60 is about two
inches long and may have a square cross section of about 0.250
millimeters per side. The length of the cooling system is about 40
millimeters, the width about 40 millimeters and the height about 7
millimeters. The pins in the evaporator chamber may be about 1
millimeter square in cross section and about 5 millimeters in
height. With such an arrangement, a Pentium brand microsystem may
have a surface temperature maintained within the range of -20 to
50.degree. C., depending on application and fluid selected.
The refrigerant is compressed in a compressor and cooled by a
condenser before entering the capillary passage 60. A heat transfer
fluid may be pumped. Thereafter, the refrigerant expands, absorbs
heat by pool boiling, forced convection or flow boiling (or a
combination of these) in the evaporator chamber 90, leaves through
the opening 68 in the base and the outlet port 36 before returning
to the compressor for the start of a new cycle. Should more heat
lift be desired, the capillary passage may be enlarged, the inlet
pressure increased, and/or the evaporator charged to a material
having a higher heat conductivity. The circulating liquid may also
be changed. If less heat lift is needed, the capillary passage size
may be reduced, the flow rate lessened, the refrigerant altered
and/or the like. Other variables may also change. There is no
intention to limit the invention here due to changes in the amount
of heat lift required or desired.
The pressure drop provided by the capillary passage is proportional
to L divided by d.sup.2 where L is length and d is hydraulic
diameter. The advantage of a design that accommodates a long
capillary passage is that the width and depth may be
proportionately larger. This is beneficial so that the passage will
be resistant to clogging. Also, a larger dimensioned passage may be
easier to consistently manufacture.
The specification describes in detail embodiments of two variations
of the present invention. Other modifications and variations will
under the doctrine of equivalents or otherwise come within the
scope of the appended claims. For example, as mentioned, enlarging
the capillary passage or making it longer or changing the
refrigerant or other liquid used to transfer heat or using aluminum
rather than cooper for the evaporator all are considered equivalent
structures. Still other alternatives will also be equivalent as
will many new technologies. There is no desire or intention here to
limit in any way the application of the doctrine of equivalents or
the scope of the claims.
* * * * *